Note: Descriptions are shown in the official language in which they were submitted.
~ CA 02231821 1998-04-14
METHOD FOR PRODUCING A LIQUID SYSTEM FOR LACTAM
POLYMERIZATION
FIELD OF THE INVENTION
The invention relates to a method for producing a liquid system for lactam
polymerization, which directly initiates and performs anionic lactam polymeriza-tion. The invention further relates to the use of the liquid system.
BACKGRO~JND OF JHE INVENTION
The activated anionic lactam polymerization is generally performed by the
~ separate addition of a catalyst and an activator to the lactam melt, wherein the
3s so-called two-pot method has gained acceptance in connection with many appli-
cations. Here, melt portions of equal volume are prepared, in which either a
- CA 02231821 1998-04-14
catalyst or an activator has been dissolved. These melts are combined for the
accelerated initiation of the polymerization. Therefore the method requires two
separate melt tanks for lactams containing dissolved substances, such as cata-
lyst or activator, which are active at higher temperatures. Therefore the storage
s stability of the melts is significantly reduced.
The polymerization of lactam could be greatly simplified and more univer-
sally applied if it were possible to omit the provision of the lactam melt, respec-
tively containing a dissolved catalyst and a dissolved activator, whereby its stor-
lO age ability is reduced. This applies in particular to lactam-12, which only be-
comes liquid above 150~C.
The situation is further complicated by the fact that catalyst and activator
must be supplied separately to the lactam melt. Thereby the catalyst generally is
s a solid, and many activators are also solids, so that polymerization must always
be preceded by separate dissolving processes, during which the polymerization
of the lactam can already start. This applies in particular to lactam-12 with its
high meltin!3 point and the introduction of catalyst into the lactam melt.
If a catalyst containing lactarn-6 is used for the polymerization of other lac-
tams, copolymerisation occurs, although only in small amounts.
Since known catalysts for lactam polymerization are solids with a limited
storage life, which for their use require a dissolving process in previously melted
2s lactam, cornplicated solvent systems have been developed for making available a
catalyst solution which is usable at least over a limited period of time, has a low
slag formal~ion tendency and preferably is liquid at room temperature. Examples
for this are German Patent DE 22 30 732 C3 and European Patent EP O 438 762
B1. However, even wlth catalyst solutions being made available, the main disad-
vantage of the method remains, namely that the activator and the catalyst must
respectively be added separately to the lactam melt for a fast and predetermableactivated anionic lactam polymerization.
- CA 02231821 1998-04-14
Thus there is a proven requirement to considerably simplify the activated
anionic lactam polymerization, to n-ake it more secure in its technical feasibility
and to perform it with fewer process steps.
The supply of a storagestable liquid system, which contains only a little or
no free lactam, which directly initiates the activated anionic lactam polymeriza-
tion and permits it to take place in a discontinuous or a continuous process,
would represent a very important technical progress.
OBJECT AND S~IMMARY OF THE INVENTION
The object of the invention therefore is a method for the production of a liq-
uid system -For initiating and performing lactam polymerization, which allows the
production of a liquid system by means of only a few method steps, in particularl5 contains no or only small amounts of free lactam and is distinguished by a low
viscosity and good storage stability, i.e. remains low viscous and active on stor-
age and, when only a small volume-fraction is added to a lactam melt, initiates,performs and terminates the lactam polymerization in a few minutes when the
temperature is suitably regulated, and therefore is qualified for continuous and20 discontinuous processes.
This object is attained by means of the method for producing a liquid cata-
lytically acting system for performing the lactam polymerization in accordance
with the ch;aracterizing features of claim 1. An other object is its preferred use in
2S processes For producing parts of polylactam and composites with a polylactam- matrix.
Produ,ction takes place by the reaction of a lactam in stoichiometric or al-
most stoichiometric proportion with a strong base in a solvatingly acting, liquid,
30 aprotic connpound, i.e. the solvating agent (S), to form a lactamate, to which an
activator is subsequently added before the solution of the resulting compound iscooled frorn the temperature to room temperature.
Further additives can then be added in any arbitrary process step.
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;
-.4.-
Thus, the inventive concept of the method for producing a liquid system for
performing the lactam polymerization lies in the inclusion of the lactamate syn-thesis in the course of producing the liquid system, consisting of a composition of
s catalyst and activator in an aprotic solvating agent, whereby the large amount
(approximately 80 weight-%) of unreacted lactam can be avoided which, in the
prior art, is used as solvent for the effective lactamate-fraction.
Solvating agents are organic compounds with aliphatic, cycloaliphatic and
aromatic structural elements, hetero atoms and hetero groups, for example:
-O-,-CO-,-SO2-,-CONR-,-COO-, -NRCOO-,-NO-, -RNCONR-, phenolether,-
NR-, P(OR)3, and PO(OR)3,
which act solvatingly.
The dashes at the structural elements mean a linkage to a radical which is
not H and cannot enter into a condensation reaction with water being split off.
R is a radical which is different from hydrogen, in particular an alkyl radical.The solvating agent can contain several of the listed structural elements.
However, the listed structural elernents should be considered to have been pro-
vided by way of example.
The solvating agent (S) is preferably an aprotic, aliphatic solvent.
Aprotic solvents are non-aqueous solvents, which do not contain an
ionizable proton in the molecule.
Preferred representatives correspond to the general formula I
RN CO NR
- (CH2)n
wherein R is an alkyl radical, in particular a methyl radical, and n = 2 and 3.
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_.5._
Further representatives are tetraalkyl urea, tetraethyl urea and tetrabutyl
urea, or N-alkylized carboxylic acid amides, for example, dialkylacetamide or di-
butylformannide, or cyclic, N- alkylized carboxylic acid amides, for example N-
alkyl pyrrolictone and N-alkyl caprolactam with preferably one alkyl radical with 1
5 to 8 C atoms, for example N-butyl-2-pyrrolidone, and in particular N-methyl pyr-
rolidone ancl N-methyl caprolactam.
In all cases the alkyl radicals can also contain hetero atoms, for example N-
(3-methyloxypropyl)-2-pyrrolidone .
Further solvating agents (S) are liquid etherized polyols, for example with a
basic structure H3C-O-(CH2-CH2-O)n-CH3 of a molecular weights up to ap-
proximately 1500, as well as esterified polyglycols, for example di- and tri-
ethylene glycol diacetate or liquid phthalic acid esters.
The solvating agent (S) requires the solvating structural elements for dis-
solving the lactam and, preferably at higher or advantageously also at room tem-peratures, t;he lactamate formed. It must be sufficiently heat-resistant to be used
as a reaction medium for the lactamate formation and subsequent reaction with
the activator to a compound and, in accordance with advantageous method vari-
ants, it must have a sufficiently high boiling point so as not to cause bubble for-
mation in the lactam melt during its subsequent use for initiating the lactam po-
lymerization. Solvating agents with boiling points between 80 and 300~C, pref-
erably at least 200~C, are advantageously used. Finally, it must dissolve the
formed compound of metal lactamate and activator at room temperature.
A method alternative, in particular for continuous polymerization process, is
a solvating agent with a low boiling point, which lies between approximately 80 to
160~C, ancl which permits the continuous removal of the solvating agent following
30 the addition of the liquid system to the lactam melt.
In further preferred variants, the solvating agent is a system of several com-
ponents of, for example, low and high boiling point, or such with different appli-
cation-specific properties. Besides a cyclic urea derivative, such a system can
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-.G.-
additionally contain, for example, a sterically hindered phenol, a fatty acid alky-
loxazoline and/or a phthalic acid ester.
In the end product, such additional components can improve, for example,
5 the resistance to heat, light and/or oxidation, or the demolding of the finished
part.
On production of the system it is possible to dissolve additional components,
which are siolids, in the main component of the solvating agent prior of starting
10 the reactiom
It is essential in connection with their selection that they do not cause undesired
side reactions during the lactamate formation and reaction with the activator and
do not, or only slightly, interfere with the subsecluent lactam polymerization.
It can be advantageous in many cases to employ a mixture of different ac-
tive solvating agents which can be mixed with each other. For example, mixtures
of cyclic ureas and/or acid amides are suitable, such as
R--N~ N--R CO N R
L(CH2)X~ L(a~2)Y~
20 wherein R is, for example methyl, and x and y are selected such that a 5-, 6- or
7-membered ring is formed.
In this case the urea group, or respectively the amide group, preferably
causes the solvating of the addition products of the lactamate to the compound A25 (carbodiimide, or respectively isocyanate), and the special polyether is used for
the further liquefaction of the system and can aid, for example, in lowering themodulus of the polylactam by means of plasticizing.
The lactams (L) employed for the lactamate formation are advantageously
30 those with 5 to 13 ring members, such as, for example butyrolactam, valerolac-
tam, caprolactam, oenantholactam and laurinelactam. Here, lactams with 5 to 7
ring members, and caprolactam in particular, are preferred.
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The strong bases (B) employed for the lactamate formation preferably havea higher basicity than the lactamate anion whose formation they cause.
s Preferclbly employed bases (B) have an alkali, earth alkali or tetraalkylam-
monium cationl and an alkoxide, amide, hydride or an alkylate as anion, or they
are Grignar~d compounds.
Examples are alkali and earth alkali metalalcoholates, in particular methylate
and ethylate, such as, for example sodium methylate and -ethylate, or alcoho-
lo lates of lithium, potassium and magnesium, or also tetraalkyl ammonium alcoho-
late, metal Ihydride, such as, for example sodium hydride, metal alkyles,, for ex-
ample such of butyl lithium, amide, such as, for example sodium amide, or also
alkali and earth alkali metals which, for example, can be activated by means of
iron(ll) ions.
1~
In spe!cial process variants the bases (B) are added as solution or suspen-
sion, for example in the solvating agent, or as small solid particles.
Carbodiimides, isocyanates and diisocyanates, which have an aliphatic, cy-
cloaliphatic, aromatic or aliphatic-aromatic base structure, are preferred activa-
tors.
Examples are liquid isocyanates, such as, for example, toluylene diisocy-
anate and hexamethylene diisocyanate, and preferably also isocyanates and di-
2s isocyanates capped with lactam, as well as carbodiimides and polycarbodiimides.
Suitable carbodiimides are, for example, N,N'-diisopropyl carbodiimide, N,N'-di-(o-tolyl)-carbodiimide, N,N'-dicyclohexyl carbodiimide, 2,2',6,6'-tetraisopropyldiphenyl carbodiimide and poly-(2,2- diisopropyl)-p-phenylene carbodiimide.
The activators can advantageously also be dissolved in the solvating agent.
Preferably 0.4 to 1 mol of the activator is used per mol of lactamate. In this
case the excess lactamate can serve to eliminate traces of residual moisture.
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Properl:y- and application-related additives (Z), which do not or only slightly
interfere with polymerization, can be advantageously added to the finished liquid
system. These are, for example, demoulding agents, defoamers, heat, light
and/or oxidation stabilizers, nucleating agents, tracers, optical brighteners, plas-
s ticizers, impact resistance agents and colorants.
In accordance with the invention, the production of the liquid system takes
place stepwise directly in the solvating agent, without it being necessary to sepa-
rate the lactamate as a solid in an intermediate stage. The method can be exer-
10 cised in many ways, depending on the initial materials selected.
The lactamate formation in solution can, for example takes place as follows:
Thereby care must be taken to assure that all components are carefully
dried. Furthermore, it is necessary to work in a protective gas.
The solvating agent is placed in a reaction vessel which can be stirred and
heated, and the lactam is dissolved at a suitable temperature. Subsequently the
base is slowly added while stirring. If in this case sodium methylate dissolved in
methanol jc, used, the alcohol added and being generated is advantageously con-
tinuously drawn off by the action of heat and vacuum, wherein following the end
20 of the addil;ion, the actions of vacuum and heat are still continued for a suitable
time while stirring. Remaining amounts of alcohol can also be removed with the
aid of an entraining agent such as, for example, tetrahydrofurane and vacuum
action.
2s Particularly strong bases such as, for example, metal hydrides (for example
NaH), or butyl lithium, or also Grignard compounds such as, for example, ethyl or
butyl magnesium chloride or also sodium amide, are often used as solution, or assuspension in a oxidation protecting agent, or like in tetrahydrofurane or dieth-
ylether. The reaction products here are volatile at room temperature, and the
30 strong bases used mostly react quite violently with the dissolved lactam. They
are advantageously added to the stirred reaction mixture in portions. If a liquid
oxidation protecting agent is used, it is subsequently removed by vacuum. It is
alternatively also possible to proceed in such a way that for example the base is
dissolved in the solvating agent or suspended therein, and thereafter the lactam3s is added while stirring, and the reaction products are drawn off by vacuum and if
CA 02231821 1998-04-14
.9.
necessary also with the aid of an entraining agent. For example, solid magne-
sium ethylate can be suspended in the solvating agent, dimethylpropylene urea,
and thereafter liquid lactam such as, for example, butyro-, valero- or oenantho-lactam can be continuously added, while the alcohol being formed is continuouslys removed by the application of vacuum and, if required, by the action of heat,
wherein an entraining agent such as, for example, tetrahydrofurane, can addi-
tionally be used. The entraining and/or the solvating agent can also be added tothe lactam, wherein it advantageously lowers the melting point of the lactam andtherefore makes it easier to meter it in.
An example is lactam-6 which, with the addition of only a small fraction of
dimethylpropylene urea, is liquid at room temperature.
In connection with the many possible variants of the method it is necessary
15 to regulate the temperature, the vacuum and to select the entraining agent ac-
cording to lhe components used. It is often advantageous to employ a solvating
agent with a boiling point of at least 200~C, advantageously of at least 230~C,
and in particular of 250~C and higher, and to select the base in such a way that it
can be easily removed from the reaction mixture after being neutralized.
It is of particular advantage in connection with the method in accordance
with the Invention for producing a liquid system for the direct initiation gof the
activated anionic lactam polymerization that it is possible to operate stoichiomet-
rically, or respectively with a minimal stoichiometric surplus of lactam, which ad-
2s vantageously lies between 1 and 10 mol-%, so that the resultant liquid system contains practically no free lactam.
In contrast thereto, solid sodium lactamate is used in the prior art, which is
composed of four parts of lactam-6 and only one part of the lactamate.
3()
It is furthermore advantageous that no free base, which could adversely af-
fect the storage stability of the system, is present in the liquid system in accor-
dance with the invention.
CA 02231821 1998-04-14
-.10.-
A further advantage is that the catalyst as an intermediate product does not
need to be isolated, and that the activator can be added directly to,the freshlyproduced, catalyst-containing solution. In the process it is advantageously
added, selectively as a solution, directly to the catalyst solution, which is kept of
70 to 120~C, for example, while stirring, whereby precipitation of the lactamate is
prevented .
Thereafter the finished liquid system is cooled to room temperature,
whereby it retains its low viscosity and remains stable in storage and can be
10 used in this form for the direct initiation and execution of the polymerization of
pure lactaml.
The polymerization of the lactam melt can be directly initiated by using the
liquid system in accordance with the invention in a continuous as well as a dis-l~ continuous process, wherein it is performed in a short time and polylactam ofhigh quality and low extract, and, which has excellent mechanical properties, isformed.
Advantageously 0.5 to 15 weight-% of the liquid system is added to the lac-
20 tam melt.
Specially suitable lactams are lactam-6 and lactam-12.
Thereby the use of the inventive liquid system for the polymerization of lac-
tam-12 is of special interest, whereby polimerization can be performed in a wide25 temperature range between 170~C to approximately 330~C, whereby the reaction
speed can be very directedly set by the selection of the temperature ranges.
A further essential advantage is that it is possible through using the method
of the invention to proceed directly from pure lactam which is stable in storage,
and the separate production of a catalyst-containing and activator- containing
30 lactam melt with its limited storage stability can be omitted. By means of this the
lactam polymerization is greatly simplified and of cost-efficiency much improved.
The application of the liquid system in accordance with the invention is of
particularly great advantage in extrusion-, injection molding-, pultrusion-, mono-
3s mer casting-, resin transfer molding-, reaction-injection molding- and rotomold-
CA 02231821 1998-04-14
-.11.-
ing-processes, as well as in the production of composit materials with polylactam
as the matrix.
The method will now be explained in more detail by means of examples.
s These do not narrow the scope of the invention, but only represent a selection of
the possibilities beeing now available.
DETAILED DESCRIPTION
For the production of the liquid system there are always used the minimum
of one of solvating agent (S), Lactam (L), base, (B) and substance activating the
polymerization (A).
1s
All these substances must be dried as thoroughly as possible. If residual
moisture is present, this may lead to the formation of a portion of precipitation in
the produced liquid system, which advantageously should be separated by de-
canting or filtration. If the amount of moisture as a whole is small, the polymeri-
zation of lactam after the addition of the liquid system is not essentially adverselyaffected. With a moisture content of the solvating agent, for example, of 0.1 to
1.0%, or by the use of insufficiently pure solvating agents which, for example,
still contain alcoholic or phenolic OH or even NH-(Zerewitinoff H), polymerization
can be greatly slowed down or completely prevented. This also applies if the
alcohol frorn neutralization remains from the reaction insufficiently removed.
In the case of lab tests, weighing of the substances was therefore performed
in a plexiglass box flooded with dry nitrogen and provided with rubber gloves and
a lock.
For testing suitable combinations of the substances S, L, B and A for pro-
30 ducing liquid systems in 100 g batches the procedure was as follows:
Solvaling agent S was heated to approximately 80~C and the lactam L dis-
solved therein. Thereafter, B (in most cases 30 weight-% of sodium methylate
dissolved in methanol) was slowly added drop-by-drop and the alcohol, corre-
~5 sponding to the solvent proportion as well as to the reaction product from the
CA 02231821 1998-04-14
,~
-.12.-
neutralization reaction of the lactam, was continuously drawn off under the con-tinuous action of a vacuum while stirring.
After the addition of the almost stoichiometric amount of alcoholate, the
s vacuum was maintained for approximately 1/2 hour while stirring, and the process
temperature was increased to 80 to 140~C, depending on the activator A used.
After breaking the vacuum, the activator A was added drop- by-drop in dry
nitrogen.
If A is a solid, such as for example in the case of many carbodiimides, mix-
ing with a small amount of S (for example 25 to 30 weight-% in relation to A) and
slight warming results in liquefaction, so that continuous addition drop-by-dropunder a blanket of dry nitrogen and stirring can take place. ~)urlng the addition
of A, the reaction solution is maintained at 80 to 100~C, and this temperature is
still maintained a further 10 minutes followed by cooling to room temperature. By
this process a stable liquid system is formed, which directly initiates the lactam
polymerization .
If a precipitation in a small amount is formed during cooling, this can be
caused by traces of water and/or impurities of the components. After the pre-
cipitation has settled, decanting or filtration can be performed, but it is also pos-
sible to take out a test amount of the supernatant clear portion for checking the
activity of the system. Tests have affirmed that using a system with a solid por-
tion, polymerization in general is only to a hardly noticeable extent negativelyaffected. Examples of a 100 9 scale are combined in Table 1.
CA 02231821 1998-04-14
-.13.-
The meaning of the abbreviations in Table 1 is as follows:
S: the solvent and solvating agent
S L: the lactam
B: the base used for neulralization
A: the activator accelerating the lactam polymerization
DMPU: dimethylpropylene urea
DMI: dimethylethylene urea
NMP: N-methyl pyrrolidone
W300: diisotridecylphthalate
MPP: methoxypropyl pyrrolidone
BH: tetrabutyl urea
TEGDE: tetraethylene glycol dimethylether
LC-4, LC-5,
LC-6: , respectively the lactam with a 5-, 6- and 7-membered ring
NaM: sodium methylate
KM: potassium methylate
MgE: magnesium diethylate
NaN: sodium amide
DCC: dicyclohexyl carbodiimide
Lox: Tetrametylene-diisocyanate capped with ricinyloxazoline
.5
IL-6: methylene diisocyanate capped with caprolactam
CD: Bis-(2,6-diisopropylphenyl) carbo-diimide
CA 0223l82l l998-04-l4
-.14.-
Table 1
EXt~
y ~ ~ ~ 3'~ ~ ~ 1~ ~D~ ~.
J~F~ 1 3 1 ~
1 DMPU 80.33 LC-6 NaM DCC 1.06:1 :1 Clear liquid, red
2 DMPU 80.00 LC-4 NaM Lox 1.20:1.1:1 lowviscosityliquid, brown, somep,~ l" lior,
3 DMPU 80.00 LC-5 NaM Lox 1.20:1.1 1 idem
4 DMI 80.33 LC-6 NaM DCC 1.05:1 :1 Clearyellowliquid
DMI 74.2 LC-6 NaM DCC 1.05:1 :1 Clearslithlyyellowliquid
6 NMP 80.33 LC-6 NaM DCC 1.05:1 :1 Clearbrown liquid
7 DMPU 40.23 LC-6 NaM DCC 1.05:1 :1 Clearbrown liquid
W300 40.00
8 NMP 75.80 LC-6 NaM DCC 1.55:1.5:1 Clear liquid, some pre t, ~t ion after 1 day
9 NMP 76.9 LC-6 NaM DCC 1.05:1.5:1 Clearstable dark-red liquid, lowviscous
DMPU 36.58 LC-6 NaM DCC 1.55:1 :1 Clear stable brown liquid
MPP 37.00
11 DMPU 79.41 LC-6 KM DCC 1.05:1 :1 Clearstablebrownliquid
12 DMPU 74.16 LC-6 MgE DCC 1 : 1 : 1 Clear yellow liquid
13 DMPU 80.33 LC-6 NaN DCC 1.05:1 :1 liquid with some pr~ lion
14 DMPU 85.33 LC-6 NaM IL-6 1.05:1 :1 Clear dark-red liquid
DMPU 71.35 LC-6 NaM CD 1.05:1 :1 Clear dark-red liquld
16 DMPU 66.65 LC-6 NaM Lox 1.05:1 :1 Clear dark-red llquid
17 TEGDE 80.00 LC-6 NaM Lox 1.30: 1.2: 1 Brown liquid, some pre.,, iOIl
18 W300 80.00 LC-6 NaM Lox 1.30 :1.2 :1 Dark-red liquid, some prt~ ,lt~lion
19 BH 80.00 LC-6 NaM Lox 1.30: 1.2: 1 Yellow liquid, some preo;~.italion
s In Table 2 polymerizations tests of lactam-12 are summarized, whereby in
all cases 3 weight-% of the respective liquid system are added.
Thereto, in each case 100 g lactam-12 were melted while stirring under a
blanket of nitrogen atmosphere, and after the predetermined temperature was
reached, the liquid system was added.
CA 02231821 1998-04-14
-.15.-
The first measured time tu is the time at which after activation of the lactam,the magnetic stirrer stops rotating. Following its quick removal, melt polymeriza-
tion is performed during the predetermined time, t. The polymer is then cooled,
comminuted and analyzed.
s
Table 2 - Polymerization Behavior
1 200 20 3.5 178 2.60 2.4
2i 2 200 20 1.0 3.31
22 3 200 20 0.5 2.71
23 4 200 20 3.5 177 2.50
24 5 200 20 2.5 176 2.5
6 200 20 4.0 176 2.53 3.33
26 7 200 20 5.0 172 2.10
27 8 200 20 3.0
28 9 200 40 4.2 176 2.80
29 10 200 20 5.0 176 2.41
11 200 20 3.5 175 2.15 6.10
31 12 240 30 16.0 164 2.17
32 13 200 20 8.0 166 1.96
33 14 170 60 0.13 nmb
34 15 200 20 0.50 177 2.55 4.60
16 200 20 0.07 172 nmb 4.30
36 17 200 20 0.13 nmb
37 18 200 20 3.5 nmb
38 19 200 20 1.0 178 1.83 3.40
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-.16.-
The meaning of the abbreviations in Table 2 is as follows:
FLS: Liquid system
T: Temperature of the mass during polymerization
t: Total polymerization time
MP,DSC: Melting point maximum meas~lred by means of the DSC method
~rel: Relative solution viscosity, m~asured as a 0.5 percent solution in
metakresol
nmb: ~rel very high, cannot be measured with conventional methods
Extract: Total extractable fraction on extraction with boiling methanol
ExamPles 39 to 47 (Table 3)
These examples contain liquid systems based on DMPU as solvating agent
(S) and are produced by means of the reaction of sodium methylate with ca-
prolactam in DMPU and subsequent addition of carbodiimide, or respectively
capped isocyanate. Production took place in accordance with the description in
connection with Examples 1 to 19.
Storage stable, reddish-brown liquids resulted in all cases, with which the
polymerization of lactam-12 can be performed with good reproducibility. Their
viscosity depends on the proportion of the components S. For example, the
product of test 45 is highly viscous, while the product in accordance with test 46
2s is of low viscosity. Viscosity can also easily be reduced by increasing the tem-
perature. For practical use the products can be heated to 100~C, briefly even upto 130~C, without their reactivity being reduced, which clearly widens the possi-
bilities of use of such systems.
- CA 02231821 1998-04-14
-.17.-
Table 3
Liquid Systems with DMPU as Solvating Agent
J~ q,
39 DMPU 66.25 CL NaM CD - 1.005 1 0.667
DMPU 75.61 CL NaM IL-6 DCC0.05:0.95 1.005 1 0.667
41 DMPU 75.52 CL NaM IL-6 DCC0.10:0.90 1.005 1 0.667
42 DMPU 75.26 CL NaM IL-6 DCC0.25:0.75 1.005 1 0.667
43 DMPU 74.78 CL NaM IL-6 DCC0.50:0.50 1.005 1 0.667
44 DMPU 70.89 CL NaM CD DCC0.50:0.50 1.005 1 0.667
DMPU 62 CL NaM CD - - 1.005 1 0.4545
46 DMPU 68.3 CL NaM CD - - 1.005 1 0.4545
47 DMPU 76.3 CL NaM IL-6 DCC0.05:0.95 1.005 1 0.667
s
The polymerization behavior of lactam-12 during on addition of the liquid
system from tests 39 to 47 is compiled in Table 4 as tests 48 to 56. For good
comparison, 3 weight-% of the liquid system was added in all the tests
A comparison of tests 48 to 51, and here in particular of the time tu, shows
that, the speed of the polymerization can be considerably affected by means of
the mixture ratio of the components A.
I5 A comparison of test 54 with test 48 further shows, that tu can also be af-
fected by means of a variation of the mixture ratio B:A. When comparing test 46
with test 45, the proportion of the solvating agent is increased. The viscosity of
the system is reduced by this. In the course of the corresponding polymerizationtests 55 and 54, changes in the behavior could hardly be noticed.
. CA 02231821 1998-04-14
-. 18 .-
ln test 56 polymerization took place at 220~C and at 240~C while maintaininga total polymerization time of 5 and 3 minutes. The measured extract values
prove that very rapid polymerization took place.
s Table 4
~ p ~ ~;r~ or;~
48 39 170 60 2.5 173 2.61 3.70
240 7 0.4 174 3.47 3.15
49 40 170 40 1.5 173 2.53
41 170 40 0.5 174 2.37
230 6 0.08 173 4.38
51 42 170 40 0.08
52 43 170 40 0.08
53 44 170 60 3.0 175 2.55
240 6 0.66 176 3.44 3.38
54 45 170 60 1.0 174 2.68
46 170 60 1.0 175 2.49
56 46 2Z0 5 2.88
240 3 2.69
Complementary tests, not listed in detail, were performed with changed pro-
10 portions of the liquid system. If in the course of this the proportion of the liquid
system is reduced, for example to 1.5 weight-%, the polymerization takes place
more slowly and simultaneously leads to higher molecular weights. If more liquidsystem is added, for example 5 weight-%, the polymerization takes place faster.
At the same time the values of ~urel are lower and therefore the molecular weight
5 is reduced.
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Test 57
s For application tests, 40 kg of the liquid system were produced from sodium
caprolactamate and DCC in DMPU, wherein sodium caprolactamate and DCC
were added at a mol ratio of 1.5: 1, and a very small lactam-6 excess was used.
Thereby, 4.15 kg lactam-6 were dissolved at 120~C in DMPU, and subse-
quently 6.58 kg of a 30-percent sodium methylate solution were slowly added
dropwize while stirring and applying a vacuum of approximately 230 mbar.
During that, methanol was continuously removed from the reaction mixture
and the temperature of the liquid system droped to approximately 90~C.
1s
At the end of the sodium methylate addition, the vacuum was increased to
50 mbar and maintained for further 30 minutes. It was then broken by means of
dry nitrogen, and 4.740 kg of DCC, dissolved in DMPU, were added while stirring.Thereafter the reaction product was cooled to 65~C and decanted into four 101
polyethylene bottles. When adding 3 weight-% of the liquid system to a lactam-
12 melt at 200~C and maintaining a polymerization time of 15 minutes, a
polyamide-12 with a melting point of 174~C, a ~rel of 2.50 and a total extract of
2.5 weight-% results.
Test 58
Using the liquid system from Test 56, polymerization was directly performed
from lactam-12 on a double-screw extruder, ZSK 30 of the Werner + Pfleiderer
company, Stuttgart (Germany) bycontinuous metering of the system into the lac-
tam melt.
For this, the twin screw extruder (I/d ratio 36) was provided with a special
screw pair, which permits the metered addition of solid lactam in the form of
3s flakes and its rapid melting,additionally continued metering-in and homogeneous
CA 0223l82l l998-04-l4
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admixing of the liquid system and thereafter continuously polymerization andconveyance of the polymer melt to the outlet nozzle. Degassing of,the melt at
several locations was complementarily provided.
s The liquid system was continuously injected into the lactam melt by meansof an oscillating reciprocating piston pump at a pressure of 15 to 20 Bar.
In order to allow injection at varying throughputs, three parts of the system
were diluted with one part of pure DMPU. This system was given the designation
FLS~.
Selected setting parameters of the test series with the double-screw ex-
truder, as well as basic analysis data of the resulting products are shown in Ta-
ble 5. Complementary to the test parameters mentioned, variations were made
in the:
rotation speed from 100 to 200 rpm,
throughput from 6.5 to 12.5 kg/h
mass-temperature of the liquid system from 70 to 130~C
concentration of FLS~ from 3 to 6 weight-%, and
temperature of the melt in the polymerization zone from 290 to 325~C.
In all cases, with the sole exception of the increased melt temperature, a
smooth, almost transparent extrusion strand resulted which, after cooling and
granulation, leads to granules which can beasely processed by injection molding
and extrusion.
In all cases where the temperature of the mass was kept below 310~C and
the FLS~ was employed in the amount of 4 weight-%, a solution viscosity of at
least 2.30, a melting point of at least 273~C and an extract of maximally 4.2
weight-% resulted, wherein it must be taken into consideration that components
of the liquid system contribute essentially to the extract.
CA 02231821 1998-04-14
TABLE 5
Throu~hput k6/h 6.5 6.~ 8.4 6.9 10.412.5
Screw speed rpm 100 100 100 100 150 100
Temperature of the Polym- ~C 290 300 290 290 290 290
erization and Conveying
Zone
Torque Nm 28 22.4 26.4 25.6 24 24,8
Amount of FLS~ Weight-% 4 4 5 6 4 4
Injection Temperature. ~C 70 70 70 70 70 70
Product Characterization
MP (DSC) ~ ~C ~ 173 173 173 172 173 175
~Jrel 0.5% mKr. 2.572.32 2.26 2.08 2.752.50
Extract (methanol) Weight.-% 3.944.18 4.79 5.09 3.443,24
ExamPle 59
This example describes the production and application of a liquid system
containing
10 additional components Z in the form of heat and light stabilizers. Thereby a FLS
of the composition in accordance with test 56 was prepared on a 100 g scale
and, following the addition of the component A (respectively in relation to the re-
sulting mass), 3 weight-% of Tinuvin 765 as the light stabilizer and 2 weight-% of
Irganox 1 135 as heat stabilizer were added, than cooling was performed and
lS subsequently 4 weight-% of this system were added to 100 g of a stirred lactam-
12 melt at 200~C. Polymerization took place in the customary manner. The stir-
CA 0223l82l l998-04-l4
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rer stopped after 1.5 minutes. After a total polymerization time of 30 minutes the
~rel was 2.527, the extract 3.18 weight % and the melting point 17~.1~C.
s Examples 59 to 64
These examples relate to the polymerization of caprolactam while using the
liquid system from Test 56.
Well dried caprolactam of so-called monomer casting quality of the Dutch
lo company DSM Fiber Intermediates BV was used and the tests performed under a
blanket of dry nitrogen.
Respectively 100 9 caprolactam were melted while being stirred by a mag-
netic stirrer, and different amounts by weight of the liquid system were added.
The tests are compiled in Table 6. The abbreviations correspond to the ones in
15 the legends of Tables 1 and 2.
As the test results prove, the liquid system produced in accordance with the
method of the invention is excellently suitable for the polymerization of lactam-6.
20 Table 6
Polymerization of Caprolactam
59 3 180 9.5 50 215.7 2.758 0.75
180 4.0 50 216.7 2.104 1.62
61 7 180 3.5 50 216.1 1.750 1.59
62 3 160 20 100 218.4 2.648 2.60
63 5 160 10.5 100 216.6 2.107 1.91
64 7 160 7.5 100 215.9 1.821 2.19
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ExamPles 65 to 73
In the following table 7 further trials are summarized.
Thereby occasionally additional activator molecules A, are used and the weight
5 fraction of the solvating agent selected in such a manner that 0.5 - 3.0 parts of
the corresponding system, added to 100 parts (weigth each) of molten lactam-12,
are sufficient to initiate and to perform its rapid and complete polimerization.
The meanings in table 7 are:
~ Components: : the raw-materials used for the synthesis
~ Comp. Molar-ratio: their molar-ratio used in the synthesis
~ S, weight-% : The weight-fraction of solvating agent of the system
15 The blocks ~Polymerization Conditions~ and ~Analysis~ have the same meaning as in ta-
ble 2.
~ LS, Parts : the weighl-fraction of Liquid-System thal is added to
the lactam-12 melt to initiate and perform its
polymerizalion.
For components A the meaning are:
~ TPC: Tripropylisocyanurate H2C
ll
~ TMI . The Isocyanate of formula: H3C - C ~C(CH3)2 - NCO
~ PHI: Phenylisocyanate
In example 65, 66, and 67 the weight-part of S is varied, whereby example 6~
contains less than 50 weight-% of solvating agent. Already at an addition of 1,13
weight-% of system 65 to the lactam melt a very good polymerization-behaviour
can be observed.
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From the system of example 66, 0,5-10 weight-% is added to the lactam-12 melt.
Thereby it becomes visible that at low addition levels. Polymerization is slow but
leads to very high molecular weights, whereby at high addition levels polimeriza-
tion is fast, whereby low molecular weights results.
s
In the examples 68-73 isocyanurate (TPC) and isocyanates were used as acti-
vator molecules.
In example 68 2 parts of sodiumcoprolactamate (NaC) per TPC were used. Adja-
10 cent trials prove that the ratio of NaC to TPC can be easely varied In the range of
1 to 3, whereby the range of 2-3 is specially suitable.
As the values of tu prove, the liquid systems, based on isocyanates, are all fast
in the initiations phase of the lactam polimerization.
15 This may be caused by the fact that in the solvating agent the lactamate, NaC,
reacts completely with the isocyanate.
Additionally it has to be mentioned that in the case of the production of isocy-anate based liquid-systems, it is possible to start directly from capped, especially
20 lactam-capped, isocyanates.
Thereby the isocyanate can at the beginning be dissolved in the solvating agent
followed by addition of the base, expl. NaM, generally in a molar-ratio, based on
isocyanate of 1:1, and followed by removing completely the neutralization product
2s of the base and optionally the solvent for the base, e.g. methanol. After cooling
down to room-temperature the system is ready and can be used.
The isocyanate based systems act in general as fast systems for the lactam po-
lymerization. Thereby the TPC-based system is of light color and leads to pure
30 white polylactam.
All these systems are specially suited for cases where the resulting melt is con-
tinuously mixed and conveyed, for example in a continuous polymerizations
process, such as in a double-screw extruder.
Table 7
Ex Components S Comp., Molar-ratio Polymerizations Cond. Analyses results
No Wt-%
S L B A L B A L S T tu t MP, DSC ,urel Extract
Parts ~C Sek Min. ~C 0,5% mK Wt.-%
65DMPU LC-6 NaM DCC48.7 1.10 1.05 1 1.13 200 118 25 176,9 2,244 4,19
66DMPU LC-6 NaM DCC61.2 1.10 1.05 1 0.50 200 630 160 173.8 4.790
1.00 200 235 60 175.8 3.044
1.50 200 150 32 2.506 1.77
2.00 200 135 27 2.207 1.77
3.00 200 90 23 1.976 1.20 ,'
5 00 200 40 10 177.Q 1.571
10.00 200 10 3 174.1 1.356
67DMPU LC-6 NaM DCC70.0 1.10 1.05 1 1.93 200 100 25 175 2.501 r
68DMPU LC-6 NaM TPC85.1 2.10 2.00 1 1t 200 20 60 170 6.90 r
69DMPU LC-6 NaM TMI75.2 1.10 1.05 1 1t 200 25 60 170 nmb
70DMPU LC-6 NaM PHi74.8 1.10 1.05 1 1t 200 15 60 174 4.9
71NMP LC-6 NaM PHI66.9 1.10 1.05 1 1t 200 7 60 174 4.1
72DMPU LC-6 NaM TMI21.6 1.10 1.05 1 1t 200 5 60 173 6.9
~ NMP 50.0
73NMP LC-6 NaM TMI77.8 1.10 1.05 1 2t 200 60 173 2.0
t For a quick and homogenous mixing, the system is prediluted with 4 parts of DMPU.--
